Cell growth and carotenoid synthesis in cultured carrot cells were examined in media with different phosphate concentrations. The growth was accelerated by increasing the P concentration and the rate of growth in the logarithmic phase was dependent on the initial concentration of phosphate. The maximum yield of the culture at the stationary phase was obtained when the additional phosphate was supplied to the culture at late logarithmic phase. Carotenoid accumulation was closely correlated to the cell growth and enhanced in P-rich medium.

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The effect of benzylaminopurine (BA) on the growth of young radish plants (Raphanus sativus L. cv. Riso Daikon) was studied and the possible role of cytokinins in the senescence of cotyledons of radish seedlings growing under water stress was examined.
1) BA application to the above-ground parts (foliage leaves, cotyledons, and hypocotyls) of plants resulted in the increase in the distribution ratio of photosynthetic product to hypocotyls and to leaves (foliage leaves and cotyledons), and the decrease in the distribution to roots. The effect of BA on the change of distribution ratio was not observed in the water-stressed plants, except for the application of higher concentrations of BA.
2) Yellowing and marked decrease in chlorophyll content were observed in the cotyledons of water-stressed plants. However, kinetin application could prevent the decrease in chlorophyll content in the cotyledons of water-stressed plants.
3) Since the decrease in chlorophyll content in the cotyledons of young radish plants with no visible foliage leaves did not occur under the water stress, yellowing may depend on the presence of growing foliage leaves.
4) Yellowing of cotyledons was observed when roots were removed but this phenomenon was not observed when kinetin was applied to the cut end of plants.
5) The cytokinin-like activity in the extract of the water-stressed plants was lower than that of the control ones.

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This paper is concerned with the temperature distribution characteristics of an open type environment controlled growth facilities of Tohoku National Agricultural Experiment Station in Morioka. Placed in a field, the equipment has three controlled factors, i.e., air temperature, soil temperature and soil moisture. The upper part of a room, however, is opened to the outdoor so that the other environmental factors, e.g., air composition, sunshine, wind, etc., are free from the control. This is the first one designed as an open type equipment in Japan. The temperature distributions in the room were measured to observe the followings.
1) Range of temperature control in the experimental rooms is less than ±2°C from the outdoor temperature.
2) The regulation of the temperature of supply air from air ducts is disturbed by the sunshine.
3) Temperature distribution takes various patterns depending on the outdoor conditions. Its major disturbances are sunshine and outdoor wind.

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The effect of air flow rate on the rate of CO₂ exchange of leaves either in the light or in the dark was studied under the various environmental conditions. The efficiency of air flow rate on photosynthesis was not so affected by temperature in the air surrounding the leaf but was greatly enhanced by increasing light intensity. The rate of CO₂ evolution in the light was stimulated by the higher rate of air flow by disturbing the reabsorption of the evolved CO₂ at the boundary layer of the leaf surface, while the rate of CO₂ evolution in the dark was not influenced by the rate of air flow because of the lack of the reabsorption. The CO₂ compensation point was also independent of the rate of air flow. Since the supply of CO₂ for photosynthesis at the compensating point of CO₂ was derived from the intracellular evolution of CO₂ by respiration, the CO₂ compensation point was not influenced by the rate of air flow.
The role of air flow rate for photosynthesis was proposed to be the supply of CO₂. The estimation of the supply of CO₂ for the leaf was done by multiplying CO₂ concentration by the triple root of air flow rate.

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In this paper, characteristics of the digital computer control of humidity in a growth-cabinet were made clear by simulation. Simulation of humidity control system on modelling of a growth-cabinet was carried out by means of hybrid computer. Sampling PID control was carried out by means of digital computer. Characteristics of K, T_I and T_D in feed-back PID algorithm of humidity were examined with τ-parameter in the simulation.
1) Value of K should be decided upon the relations with manipulating capacity P or τ. Computer control of humidity should be programmed in consideration of proper value of K in steady-state condition or in transient condition.
2) Optimum value of T_I was 200 sec in transient condition. In steady-state condition, optimum value of T_I should be smaller.
3) Values of T_D should be optimum in the next relation; 3 sec≤T_D≤20 sec.
4) Time constant of detecting means was examined with the relation of P and K. In large time constant of detecting means, stability of humidity control could be allowable on the condition of optimum K and P.

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The purpose of the present study is to throw light on the genetical control of phototactic behaviors in the silkworm, Bombix mori.
Different four silkworm strains showing clear cut differential walking responses to light at the stage of mounting in cocooning frames under a light condition in an ordinary rearing room have been analyzed their phototactic behaviors throughout the whole larval stages. Among the tested four strains, two mutant strains, nb and pe; ok, were of photopositive and the other two strains, st and Ze; pe; re, were of photonegative. The larval phototactic behavior was measured by a mean walking distance (in centimeter) from the start line to either light or dark parts in a silkworm phototactic measurement apparatus (Fig. 1) .
The result of experiments indicated that a remarkable phototactic response is observed at the stage of mature larvae, but no significant response is observed in other larval stages. At the stage of matured larvae phototactic behaviors of the tested four strains were parallel with those of each strain at the mounting stage. Not yet completed analyses, however, the result of cross experiments between photopositive and negative strains showed that larval phototactic behaviors of F₁ (or F₂) hybrids seem to cover both parental behaviors. Though the tendency of the larval phototactic behavior of F₁ (or F₂) hybrids was somewhat photonegative rather than neutral, regardless of parent.
These findings may suggest that the nature of larval photonegative characters in the silkworm is more or less dominance than that of photopositive ones and factor (s) manifesting the larval phototactic character is controlled by polygenes.

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